There is a conversation we have regularly with mining clients — usually after something has gone wrong. It goes something like this: the EEM program has been running for a cycle or two, an effect has been identified in the receiving environment, and now the mine is facing an investigation of cause process that suggests the mine is negatively affecting the environment.
In many of those cases, the problem was not the mine’s effluent. The problem was that the monitoring program had no way to prove it.
That is what pre-trigger baseline sampling is designed to prevent. And in our experience, it is one of the most cost-effective investments a mining project can make before MDMER kicks in.
What baseline sampling involves
Baseline sampling means collecting environmental data at your proposed EEM monitoring locations before your mine begins discharging effluent and the MDMER is triggered.
This data characterises the natural condition of the receiving environment: the fish community, the benthic invertebrate community, water quality parameters. It establishes what ‘normal’ looks like at each sampling area before the mine has any influence on it.
The approach that makes this most powerful is what scientists call a Before-After-Control-Impact (BACI) design. Rather than simply comparing an ‘impact’ (exposed) area (a Control-Impact or CI approach), BACI uses data from before and after the mine begins operating from both of these areas. This gives you a much stronger scientific foundation for determining whether any observed changes are genuinely mine-related — or simply natural differences between Impact and Control areas.
Why it matters: the false effect problem
Here is the challenge with EEM programs that start without pre-trigger baseline data.
Receiving environments are not static — . A typical EEM design compares an exposed area (downstream of the effluent discharge) to a reference area selected to be as similar as possible to exposed conditions, but no two areas are ever identical Fish populations fluctuate. Benthic invertebrate communities shift with seasonal changes, upstream land use, natural disturbance events. If your EEM program begins at the point of the MDMER trigger — with no data from before operations — it has no way to distinguish between differences that were always there and differences that the mine may have caused. Under EEM,
When an ‘effect’ is identified and confirmed under a CI design, the result is an investigation of cause process. IOC studies are more expensive, time-consuming, and technically demanding than “routine” studies. They also draw regulatory attention that most operators would prefer to avoid.
Pre-trigger baseline data is the scientific insurance policy that can prevent that scenario. It can prevent the potential misattribution of simple differences as being effluent-related effects.
The cost argument
Baseline sampling before MDMER trigger is not free — it requires field work, laboratory analysis, and data management. But can be substantially cheaper than the alternative.
An IOC study involves additional field sampling, detailed cause-and-effect analysis, and a more intensive interpretive reporting process. Depending on the scale of the mine and the nature of the effect, an IOC process can add significant time and cost to an EEM program that could have been avoided with the collection of suitable baseline data.
More importantly, baseline data collected before operations begin only gets more valuable over time. It is data you can never go back and collect once the mine is running.
When to start
The ideal time to begin baseline data collection is during the baseline monitoring phase of the project — before construction begins, and before MDMER trigger. This aligns with the environmental baseline studies that should already be happening as part of the EA process.
If baseline collection is designed with future EEM needs in mind from the start — using the same sampling locations, the same parameters, the same protocols — that data becomes directly usable in the EEM program. No duplication of effort. No data gaps.
The mines that navigate EEM most efficiently are the ones that started thinking about it before they had to.
What this means in practice
If your project is in the baseline, planning, environmental assessment, or early permitting phase, now is the time to have a conversation about EEM baseline design. Specifically:
- Are your proposed monitoring locations aligned with where EEM sampling will be required?
- Are the parameters you are collecting now the ones that will be needed for the EEM study design?
- Is your sampling design set up to support a BACI approach — with sufficient replication across sites and time periods?
Getting these questions answered early does not add significant cost to the baseline program. Not getting them answered can add significant cost to the EEM program that follows.
About the author
Kevin Martens is a Principal Aquatic Scientist with Trinity Consultants Canada and has been implementing EEM studies across Canada for over 20 years. He has conducted field sampling for EEM programs at more than 25 mines, has been preparing EEM study designs and interpretive reports for 15 years, provides senior oversight and review for current EEMs conducted by Trinity Consultants Canada, and still gets into the field to conduct sampling for these studies. Kevin has extensive knowledge of the MDMER and experience in understanding what sampling methods are best suited for various sampling environments. In addition to EEM sampling and reporting, Kevin supports clients with developing and implementing baseline monitoring programs that will support future EEM studies, and with implementing studies to support EEM work, such as plume delineation and modelling studies and toxicity testing.
